Nanoscale morphological control of anode electrodes by grafting of methylsulfonic acid groups onto platinum-ruthenium-supported carbon blacks

An increase in catalyst utilization in direct methanol fuel cells (DMFCs) is necessary to improve performance and reduce costs. We propose an electrode fabrication method, based on the process of grafting a proton-conducting agent onto catalyst-supported carbons before the conventional electrode fabrication process where catalyst-supported carbons are simply mixed with the perfluorosulfonic ionomer. In this study, methylsulfonic acid groups (-CH2SO3H) as proton-conducting agents have been successfully introduced to the pores of catalyst-supported carbons. We found that the chemical connections between the grafted methylsulfonic acid groups and the surface of catalyst-supported carbons were stable up to around 380 degrees C. Furthermore, by morphological analysis, we found that the grafted methylsulfonic acid groups were homogeneously introduced into both the primary and the secondary pores, and produced no significant structural change in the secondary pore that could affect the mass transfer process. The DMFC performance of the membrane electrode assembly (MEA) made using our grafting method was superior to that of an MEA made using the conventional method. A maximum power density of 87 mW cm(-2) was obtained by using grafted catalyst-supported carbons at an anode electrode in the DMFC in the low Pt-Ru loading amount of ca. 0.7 mg cm(-2) (Pt loading amount: ca. 0.5 mg cm(-2)) at 50 degrees C under atmospheric pressure. (c) 2006 The Electrochemical Society.